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openssh-portable/auth.c

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/* $OpenBSD: auth.c,v 1.152 2021/04/03 06:18:40 djm Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "includes.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#ifdef HAVE_PATHS_H
# include <paths.h>
#endif
#include <pwd.h>
#ifdef HAVE_LOGIN_H
#include <login.h>
#endif
#ifdef USE_SHADOW
#include <shadow.h>
#endif
#include <stdarg.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#include <netdb.h>
#include <time.h>
#include "xmalloc.h"
#include "match.h"
#include "groupaccess.h"
#include "log.h"
#include "sshbuf.h"
#include "misc.h"
#include "servconf.h"
#include "sshkey.h"
#include "hostfile.h"
#include "auth.h"
#include "auth-options.h"
#include "canohost.h"
#include "uidswap.h"
#include "packet.h"
#include "loginrec.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "authfile.h"
#include "monitor_wrap.h"
#include "ssherr.h"
#include "compat.h"
#include "channels.h"
/* import */
extern ServerOptions options;
extern struct include_list includes;
extern int use_privsep;
extern struct sshbuf *loginmsg;
extern struct passwd *privsep_pw;
extern struct sshauthopt *auth_opts;
/* Debugging messages */
static struct sshbuf *auth_debug;
/*
* Check if the user is allowed to log in via ssh. If user is listed
* in DenyUsers or one of user's groups is listed in DenyGroups, false
* will be returned. If AllowUsers isn't empty and user isn't listed
* there, or if AllowGroups isn't empty and one of user's groups isn't
* listed there, false will be returned.
* If the user's shell is not executable, false will be returned.
* Otherwise true is returned.
*/
int
allowed_user(struct ssh *ssh, struct passwd * pw)
{
struct stat st;
const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL;
u_int i;
int r;
#ifdef USE_SHADOW
struct spwd *spw = NULL;
#endif
/* Shouldn't be called if pw is NULL, but better safe than sorry... */
if (!pw || !pw->pw_name)
return 0;
#ifdef USE_SHADOW
if (!options.use_pam)
spw = getspnam(pw->pw_name);
#ifdef HAS_SHADOW_EXPIRE
if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw))
return 0;
#endif /* HAS_SHADOW_EXPIRE */
#endif /* USE_SHADOW */
/* grab passwd field for locked account check */
passwd = pw->pw_passwd;
#ifdef USE_SHADOW
if (spw != NULL)
#ifdef USE_LIBIAF
passwd = get_iaf_password(pw);
#else
passwd = spw->sp_pwdp;
#endif /* USE_LIBIAF */
#endif
/* check for locked account */
if (!options.use_pam && passwd && *passwd) {
int locked = 0;
#ifdef LOCKED_PASSWD_STRING
if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0)
locked = 1;
#endif
#ifdef LOCKED_PASSWD_PREFIX
if (strncmp(passwd, LOCKED_PASSWD_PREFIX,
strlen(LOCKED_PASSWD_PREFIX)) == 0)
locked = 1;
#endif
#ifdef LOCKED_PASSWD_SUBSTR
if (strstr(passwd, LOCKED_PASSWD_SUBSTR))
locked = 1;
#endif
#ifdef USE_LIBIAF
free((void *) passwd);
#endif /* USE_LIBIAF */
if (locked) {
logit("User %.100s not allowed because account is locked",
pw->pw_name);
return 0;
}
}
/*
* Deny if shell does not exist or is not executable unless we
* are chrooting.
*/
if (options.chroot_directory == NULL ||
strcasecmp(options.chroot_directory, "none") == 0) {
char *shell = xstrdup((pw->pw_shell[0] == '\0') ?
_PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */
if (stat(shell, &st) == -1) {
logit("User %.100s not allowed because shell %.100s "
"does not exist", pw->pw_name, shell);
free(shell);
return 0;
}
if (S_ISREG(st.st_mode) == 0 ||
(st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
logit("User %.100s not allowed because shell %.100s "
"is not executable", pw->pw_name, shell);
free(shell);
return 0;
}
free(shell);
}
if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
options.num_deny_groups > 0 || options.num_allow_groups > 0) {
hostname = auth_get_canonical_hostname(ssh, options.use_dns);
ipaddr = ssh_remote_ipaddr(ssh);
}
/* Return false if user is listed in DenyUsers */
if (options.num_deny_users > 0) {
for (i = 0; i < options.num_deny_users; i++) {
r = match_user(pw->pw_name, hostname, ipaddr,
options.deny_users[i]);
if (r < 0) {
fatal("Invalid DenyUsers pattern \"%.100s\"",
options.deny_users[i]);
} else if (r != 0) {
logit("User %.100s from %.100s not allowed "
"because listed in DenyUsers",
pw->pw_name, hostname);
return 0;
}
}
}
/* Return false if AllowUsers isn't empty and user isn't listed there */
if (options.num_allow_users > 0) {
for (i = 0; i < options.num_allow_users; i++) {
r = match_user(pw->pw_name, hostname, ipaddr,
options.allow_users[i]);
if (r < 0) {
fatal("Invalid AllowUsers pattern \"%.100s\"",
options.allow_users[i]);
} else if (r == 1)
break;
}
/* i < options.num_allow_users iff we break for loop */
if (i >= options.num_allow_users) {
logit("User %.100s from %.100s not allowed because "
"not listed in AllowUsers", pw->pw_name, hostname);
return 0;
}
}
if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
/* Get the user's group access list (primary and supplementary) */
if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
logit("User %.100s from %.100s not allowed because "
"not in any group", pw->pw_name, hostname);
return 0;
}
/* Return false if one of user's groups is listed in DenyGroups */
if (options.num_deny_groups > 0)
if (ga_match(options.deny_groups,
options.num_deny_groups)) {
ga_free();
logit("User %.100s from %.100s not allowed "
"because a group is listed in DenyGroups",
pw->pw_name, hostname);
return 0;
}
/*
* Return false if AllowGroups isn't empty and one of user's groups
* isn't listed there
*/
if (options.num_allow_groups > 0)
if (!ga_match(options.allow_groups,
options.num_allow_groups)) {
ga_free();
logit("User %.100s from %.100s not allowed "
"because none of user's groups are listed "
"in AllowGroups", pw->pw_name, hostname);
return 0;
}
ga_free();
}
#ifdef CUSTOM_SYS_AUTH_ALLOWED_USER
if (!sys_auth_allowed_user(pw, loginmsg))
return 0;
#endif
/* We found no reason not to let this user try to log on... */
return 1;
}
/*
* Formats any key left in authctxt->auth_method_key for inclusion in
* auth_log()'s message. Also includes authxtct->auth_method_info if present.
*/
static char *
format_method_key(Authctxt *authctxt)
{
const struct sshkey *key = authctxt->auth_method_key;
const char *methinfo = authctxt->auth_method_info;
char *fp, *cafp, *ret = NULL;
if (key == NULL)
return NULL;
if (sshkey_is_cert(key)) {
fp = sshkey_fingerprint(key,
options.fingerprint_hash, SSH_FP_DEFAULT);
cafp = sshkey_fingerprint(key->cert->signature_key,
options.fingerprint_hash, SSH_FP_DEFAULT);
xasprintf(&ret, "%s %s ID %s (serial %llu) CA %s %s%s%s",
sshkey_type(key), fp == NULL ? "(null)" : fp,
key->cert->key_id,
(unsigned long long)key->cert->serial,
sshkey_type(key->cert->signature_key),
cafp == NULL ? "(null)" : cafp,
methinfo == NULL ? "" : ", ",
methinfo == NULL ? "" : methinfo);
free(fp);
free(cafp);
} else {
fp = sshkey_fingerprint(key, options.fingerprint_hash,
SSH_FP_DEFAULT);
xasprintf(&ret, "%s %s%s%s", sshkey_type(key),
fp == NULL ? "(null)" : fp,
methinfo == NULL ? "" : ", ",
methinfo == NULL ? "" : methinfo);
free(fp);
}
return ret;
}
void
auth_log(struct ssh *ssh, int authenticated, int partial,
const char *method, const char *submethod)
{
Authctxt *authctxt = (Authctxt *)ssh->authctxt;
int level = SYSLOG_LEVEL_VERBOSE;
const char *authmsg;
char *extra = NULL;
if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
return;
/* Raise logging level */
if (authenticated == 1 ||
!authctxt->valid ||
authctxt->failures >= options.max_authtries / 2 ||
strcmp(method, "password") == 0)
level = SYSLOG_LEVEL_INFO;
if (authctxt->postponed)
authmsg = "Postponed";
else if (partial)
authmsg = "Partial";
else
authmsg = authenticated ? "Accepted" : "Failed";
if ((extra = format_method_key(authctxt)) == NULL) {
if (authctxt->auth_method_info != NULL)
extra = xstrdup(authctxt->auth_method_info);
}
do_log2(level, "%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s",
authmsg,
method,
submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod,
authctxt->valid ? "" : "invalid user ",
authctxt->user,
ssh_remote_ipaddr(ssh),
ssh_remote_port(ssh),
extra != NULL ? ": " : "",
extra != NULL ? extra : "");
free(extra);
#ifdef CUSTOM_FAILED_LOGIN
if (authenticated == 0 && !authctxt->postponed &&
(strcmp(method, "password") == 0 ||
strncmp(method, "keyboard-interactive", 20) == 0 ||
strcmp(method, "challenge-response") == 0))
record_failed_login(ssh, authctxt->user,
auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
# ifdef WITH_AIXAUTHENTICATE
if (authenticated)
sys_auth_record_login(authctxt->user,
auth_get_canonical_hostname(ssh, options.use_dns), "ssh",
loginmsg);
# endif
#endif
#ifdef SSH_AUDIT_EVENTS
if (authenticated == 0 && !authctxt->postponed)
audit_event(ssh, audit_classify_auth(method));
#endif
}
void
auth_maxtries_exceeded(struct ssh *ssh)
{
Authctxt *authctxt = (Authctxt *)ssh->authctxt;
error("maximum authentication attempts exceeded for "
"%s%.100s from %.200s port %d ssh2",
authctxt->valid ? "" : "invalid user ",
authctxt->user,
ssh_remote_ipaddr(ssh),
ssh_remote_port(ssh));
ssh_packet_disconnect(ssh, "Too many authentication failures");
/* NOTREACHED */
}
/*
* Check whether root logins are disallowed.
*/
int
auth_root_allowed(struct ssh *ssh, const char *method)
{
switch (options.permit_root_login) {
case PERMIT_YES:
return 1;
case PERMIT_NO_PASSWD:
if (strcmp(method, "publickey") == 0 ||
strcmp(method, "hostbased") == 0 ||
strcmp(method, "gssapi-with-mic") == 0)
return 1;
break;
case PERMIT_FORCED_ONLY:
if (auth_opts->force_command != NULL) {
logit("Root login accepted for forced command.");
return 1;
}
break;
}
logit("ROOT LOGIN REFUSED FROM %.200s port %d",
ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
return 0;
}
/*
* Given a template and a passwd structure, build a filename
* by substituting % tokenised options. Currently, %% becomes '%',
* %h becomes the home directory and %u the username.
*
* This returns a buffer allocated by xmalloc.
*/
char *
expand_authorized_keys(const char *filename, struct passwd *pw)
{
char *file, uidstr[32], ret[PATH_MAX];
int i;
snprintf(uidstr, sizeof(uidstr), "%llu",
(unsigned long long)pw->pw_uid);
file = percent_expand(filename, "h", pw->pw_dir,
"u", pw->pw_name, "U", uidstr, (char *)NULL);
/*
* Ensure that filename starts anchored. If not, be backward
* compatible and prepend the '%h/'
*/
if (path_absolute(file))
return (file);
i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
if (i < 0 || (size_t)i >= sizeof(ret))
fatal("expand_authorized_keys: path too long");
free(file);
return (xstrdup(ret));
}
char *
authorized_principals_file(struct passwd *pw)
{
if (options.authorized_principals_file == NULL)
return NULL;
return expand_authorized_keys(options.authorized_principals_file, pw);
}
/* return ok if key exists in sysfile or userfile */
HostStatus
check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host,
const char *sysfile, const char *userfile)
{
char *user_hostfile;
struct stat st;
HostStatus host_status;
struct hostkeys *hostkeys;
const struct hostkey_entry *found;
hostkeys = init_hostkeys();
load_hostkeys(hostkeys, host, sysfile, 0);
if (userfile != NULL) {
user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
if (options.strict_modes &&
(stat(user_hostfile, &st) == 0) &&
((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
(st.st_mode & 022) != 0)) {
logit("Authentication refused for %.100s: "
"bad owner or modes for %.200s",
pw->pw_name, user_hostfile);
auth_debug_add("Ignored %.200s: bad ownership or modes",
user_hostfile);
} else {
temporarily_use_uid(pw);
load_hostkeys(hostkeys, host, user_hostfile, 0);
restore_uid();
}
free(user_hostfile);
}
host_status = check_key_in_hostkeys(hostkeys, key, &found);
if (host_status == HOST_REVOKED)
error("WARNING: revoked key for %s attempted authentication",
host);
else if (host_status == HOST_OK)
debug_f("key for %s found at %s:%ld",
found->host, found->file, found->line);
else
debug_f("key for host %s not found", host);
free_hostkeys(hostkeys);
return host_status;
}
static FILE *
auth_openfile(const char *file, struct passwd *pw, int strict_modes,
int log_missing, char *file_type)
{
char line[1024];
struct stat st;
int fd;
FILE *f;
if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) {
if (log_missing || errno != ENOENT)
debug("Could not open %s '%s': %s", file_type, file,
strerror(errno));
return NULL;
}
if (fstat(fd, &st) == -1) {
close(fd);
return NULL;
}
if (!S_ISREG(st.st_mode)) {
logit("User %s %s %s is not a regular file",
pw->pw_name, file_type, file);
close(fd);
return NULL;
}
unset_nonblock(fd);
if ((f = fdopen(fd, "r")) == NULL) {
close(fd);
return NULL;
}
if (strict_modes &&
safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) {
fclose(f);
logit("Authentication refused: %s", line);
auth_debug_add("Ignored %s: %s", file_type, line);
return NULL;
}
return f;
}
FILE *
auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes)
{
return auth_openfile(file, pw, strict_modes, 1, "authorized keys");
}
FILE *
auth_openprincipals(const char *file, struct passwd *pw, int strict_modes)
{
return auth_openfile(file, pw, strict_modes, 0,
"authorized principals");
}
struct passwd *
getpwnamallow(struct ssh *ssh, const char *user)
{
#ifdef HAVE_LOGIN_CAP
extern login_cap_t *lc;
#ifdef BSD_AUTH
auth_session_t *as;
#endif
#endif
struct passwd *pw;
struct connection_info *ci;
u_int i;
ci = get_connection_info(ssh, 1, options.use_dns);
ci->user = user;
parse_server_match_config(&options, &includes, ci);
log_change_level(options.log_level);
log_verbose_reset();
for (i = 0; i < options.num_log_verbose; i++)
log_verbose_add(options.log_verbose[i]);
process_permitopen(ssh, &options);
#if defined(_AIX) && defined(HAVE_SETAUTHDB)
aix_setauthdb(user);
#endif
pw = getpwnam(user);
#if defined(_AIX) && defined(HAVE_SETAUTHDB)
aix_restoreauthdb();
#endif
if (pw == NULL) {
logit("Invalid user %.100s from %.100s port %d",
user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
#ifdef CUSTOM_FAILED_LOGIN
record_failed_login(ssh, user,
auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
#endif
#ifdef SSH_AUDIT_EVENTS
audit_event(ssh, SSH_INVALID_USER);
#endif /* SSH_AUDIT_EVENTS */
return (NULL);
}
if (!allowed_user(ssh, pw))
return (NULL);
#ifdef HAVE_LOGIN_CAP
if ((lc = login_getpwclass(pw)) == NULL) {
debug("unable to get login class: %s", user);
return (NULL);
}
#ifdef BSD_AUTH
if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
debug("Approval failure for %s", user);
pw = NULL;
}
if (as != NULL)
auth_close(as);
#endif
#endif
if (pw != NULL)
return (pwcopy(pw));
return (NULL);
}
/* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
int
auth_key_is_revoked(struct sshkey *key)
{
char *fp = NULL;
int r;
if (options.revoked_keys_file == NULL)
return 0;
if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
SSH_FP_DEFAULT)) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
error_fr(r, "fingerprint key");
goto out;
}
r = sshkey_check_revoked(key, options.revoked_keys_file);
switch (r) {
case 0:
break; /* not revoked */
case SSH_ERR_KEY_REVOKED:
error("Authentication key %s %s revoked by file %s",
sshkey_type(key), fp, options.revoked_keys_file);
goto out;
default:
error_r(r, "Error checking authentication key %s %s in "
"revoked keys file %s", sshkey_type(key), fp,
options.revoked_keys_file);
goto out;
}
/* Success */
r = 0;
out:
free(fp);
return r == 0 ? 0 : 1;
}
void
auth_debug_add(const char *fmt,...)
{
char buf[1024];
va_list args;
int r;
if (auth_debug == NULL)
return;
va_start(args, fmt);
vsnprintf(buf, sizeof(buf), fmt, args);
va_end(args);
if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0)
fatal_fr(r, "sshbuf_put_cstring");
}
void
auth_debug_send(struct ssh *ssh)
{
char *msg;
int r;
if (auth_debug == NULL)
return;
while (sshbuf_len(auth_debug) != 0) {
if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0)
fatal_fr(r, "sshbuf_get_cstring");
ssh_packet_send_debug(ssh, "%s", msg);
free(msg);
}
}
void
auth_debug_reset(void)
{
if (auth_debug != NULL)
sshbuf_reset(auth_debug);
else if ((auth_debug = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
}
struct passwd *
fakepw(void)
{
static struct passwd fake;
memset(&fake, 0, sizeof(fake));
fake.pw_name = "NOUSER";
fake.pw_passwd =
"$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
#ifdef HAVE_STRUCT_PASSWD_PW_GECOS
fake.pw_gecos = "NOUSER";
#endif
fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid;
fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid;
#ifdef HAVE_STRUCT_PASSWD_PW_CLASS
fake.pw_class = "";
#endif
fake.pw_dir = "/nonexist";
fake.pw_shell = "/nonexist";
return (&fake);
}
/*
* Returns the remote DNS hostname as a string. The returned string must not
* be freed. NB. this will usually trigger a DNS query the first time it is
* called.
* This function does additional checks on the hostname to mitigate some
* attacks on legacy rhosts-style authentication.
* XXX is RhostsRSAAuthentication vulnerable to these?
* XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?)
*/
static char *
remote_hostname(struct ssh *ssh)
{
struct sockaddr_storage from;
socklen_t fromlen;
struct addrinfo hints, *ai, *aitop;
char name[NI_MAXHOST], ntop2[NI_MAXHOST];
const char *ntop = ssh_remote_ipaddr(ssh);
/* Get IP address of client. */
fromlen = sizeof(from);
memset(&from, 0, sizeof(from));
if (getpeername(ssh_packet_get_connection_in(ssh),
(struct sockaddr *)&from, &fromlen) == -1) {
debug("getpeername failed: %.100s", strerror(errno));
return xstrdup(ntop);
}
ipv64_normalise_mapped(&from, &fromlen);
if (from.ss_family == AF_INET6)
fromlen = sizeof(struct sockaddr_in6);
debug3("Trying to reverse map address %.100s.", ntop);
/* Map the IP address to a host name. */
if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
NULL, 0, NI_NAMEREQD) != 0) {
/* Host name not found. Use ip address. */
return xstrdup(ntop);
}
/*
* if reverse lookup result looks like a numeric hostname,
* someone is trying to trick us by PTR record like following:
* 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
*/
memset(&hints, 0, sizeof(hints));
hints.ai_socktype = SOCK_DGRAM; /*dummy*/
hints.ai_flags = AI_NUMERICHOST;
if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
name, ntop);
freeaddrinfo(ai);
return xstrdup(ntop);
}
/* Names are stored in lowercase. */
lowercase(name);
/*
* Map it back to an IP address and check that the given
* address actually is an address of this host. This is
* necessary because anyone with access to a name server can
* define arbitrary names for an IP address. Mapping from
* name to IP address can be trusted better (but can still be
* fooled if the intruder has access to the name server of
* the domain).
*/
memset(&hints, 0, sizeof(hints));
hints.ai_family = from.ss_family;
hints.ai_socktype = SOCK_STREAM;
if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
logit("reverse mapping checking getaddrinfo for %.700s "
"[%s] failed.", name, ntop);
return xstrdup(ntop);
}
/* Look for the address from the list of addresses. */
for (ai = aitop; ai; ai = ai->ai_next) {
if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
(strcmp(ntop, ntop2) == 0))
break;
}
freeaddrinfo(aitop);
/* If we reached the end of the list, the address was not there. */
if (ai == NULL) {
/* Address not found for the host name. */
logit("Address %.100s maps to %.600s, but this does not "
"map back to the address.", ntop, name);
return xstrdup(ntop);
}
return xstrdup(name);
}
/*
* Return the canonical name of the host in the other side of the current
* connection. The host name is cached, so it is efficient to call this
* several times.
*/
const char *
auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
{
static char *dnsname;
if (!use_dns)
return ssh_remote_ipaddr(ssh);
else if (dnsname != NULL)
return dnsname;
else {
dnsname = remote_hostname(ssh);
return dnsname;
}
}
/* These functions link key/cert options to the auth framework */
/* Log sshauthopt options locally and (optionally) for remote transmission */
void
auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote)
{
int do_env = options.permit_user_env && opts->nenv > 0;
int do_permitopen = opts->npermitopen > 0 &&
(options.allow_tcp_forwarding & FORWARD_LOCAL) != 0;
int do_permitlisten = opts->npermitlisten > 0 &&
(options.allow_tcp_forwarding & FORWARD_REMOTE) != 0;
size_t i;
char msg[1024], buf[64];
snprintf(buf, sizeof(buf), "%d", opts->force_tun_device);
/* Try to keep this alphabetically sorted */
snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s",
opts->permit_agent_forwarding_flag ? " agent-forwarding" : "",
opts->force_command == NULL ? "" : " command",
do_env ? " environment" : "",
opts->valid_before == 0 ? "" : "expires",
opts->no_require_user_presence ? " no-touch-required" : "",
do_permitopen ? " permitopen" : "",
do_permitlisten ? " permitlisten" : "",
opts->permit_port_forwarding_flag ? " port-forwarding" : "",
opts->cert_principals == NULL ? "" : " principals",
opts->permit_pty_flag ? " pty" : "",
opts->require_verify ? " uv" : "",
opts->force_tun_device == -1 ? "" : " tun=",
opts->force_tun_device == -1 ? "" : buf,
opts->permit_user_rc ? " user-rc" : "",
opts->permit_x11_forwarding_flag ? " x11-forwarding" : "");
debug("%s: %s", loc, msg);
if (do_remote)
auth_debug_add("%s: %s", loc, msg);
if (options.permit_user_env) {
for (i = 0; i < opts->nenv; i++) {
debug("%s: environment: %s", loc, opts->env[i]);
if (do_remote) {
auth_debug_add("%s: environment: %s",
loc, opts->env[i]);
}
}
}
/* Go into a little more details for the local logs. */
if (opts->valid_before != 0) {
format_absolute_time(opts->valid_before, buf, sizeof(buf));
debug("%s: expires at %s", loc, buf);
}
if (opts->cert_principals != NULL) {
debug("%s: authorized principals: \"%s\"",
loc, opts->cert_principals);
}
if (opts->force_command != NULL)
debug("%s: forced command: \"%s\"", loc, opts->force_command);
if (do_permitopen) {
for (i = 0; i < opts->npermitopen; i++) {
debug("%s: permitted open: %s",
loc, opts->permitopen[i]);
}
}
if (do_permitlisten) {
for (i = 0; i < opts->npermitlisten; i++) {
debug("%s: permitted listen: %s",
loc, opts->permitlisten[i]);
}
}
}
/* Activate a new set of key/cert options; merging with what is there. */
int
auth_activate_options(struct ssh *ssh, struct sshauthopt *opts)
{
struct sshauthopt *old = auth_opts;
const char *emsg = NULL;
debug_f("setting new authentication options");
if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) {
error("Inconsistent authentication options: %s", emsg);
return -1;
}
return 0;
}
/* Disable forwarding, etc for the session */
void
auth_restrict_session(struct ssh *ssh)
{
struct sshauthopt *restricted;
debug_f("restricting session");
/* A blank sshauthopt defaults to permitting nothing */
restricted = sshauthopt_new();
restricted->permit_pty_flag = 1;
restricted->restricted = 1;
if (auth_activate_options(ssh, restricted) != 0)
fatal_f("failed to restrict session");
sshauthopt_free(restricted);
}
int
auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw,
struct sshauthopt *opts, int allow_cert_authority, const char *loc)
{
const char *remote_ip = ssh_remote_ipaddr(ssh);
const char *remote_host = auth_get_canonical_hostname(ssh,
options.use_dns);
time_t now = time(NULL);
char buf[64];
/*
* Check keys/principals file expiry time.
* NB. validity interval in certificate is handled elsewhere.
*/
if (opts->valid_before && now > 0 &&
opts->valid_before < (uint64_t)now) {
format_absolute_time(opts->valid_before, buf, sizeof(buf));
debug("%s: entry expired at %s", loc, buf);
auth_debug_add("%s: entry expired at %s", loc, buf);
return -1;
}
/* Consistency checks */
if (opts->cert_principals != NULL && !opts->cert_authority) {
debug("%s: principals on non-CA key", loc);
auth_debug_add("%s: principals on non-CA key", loc);
/* deny access */
return -1;
}
/* cert-authority flag isn't valid in authorized_principals files */
if (!allow_cert_authority && opts->cert_authority) {
debug("%s: cert-authority flag invalid here", loc);
auth_debug_add("%s: cert-authority flag invalid here", loc);
/* deny access */
return -1;
}
/* Perform from= checks */
if (opts->required_from_host_keys != NULL) {
switch (match_host_and_ip(remote_host, remote_ip,
opts->required_from_host_keys )) {
case 1:
/* Host name matches. */
break;
case -1:
default:
debug("%s: invalid from criteria", loc);
auth_debug_add("%s: invalid from criteria", loc);
/* FALLTHROUGH */
case 0:
logit("%s: Authentication tried for %.100s with "
"correct key but not from a permitted "
"host (host=%.200s, ip=%.200s, required=%.200s).",
loc, pw->pw_name, remote_host, remote_ip,
opts->required_from_host_keys);
auth_debug_add("%s: Your host '%.200s' is not "
"permitted to use this key for login.",
loc, remote_host);
/* deny access */
return -1;
}
}
/* Check source-address restriction from certificate */
if (opts->required_from_host_cert != NULL) {
switch (addr_match_cidr_list(remote_ip,
opts->required_from_host_cert)) {
case 1:
/* accepted */
break;
case -1:
default:
/* invalid */
error("%s: Certificate source-address invalid", loc);
/* FALLTHROUGH */
case 0:
logit("%s: Authentication tried for %.100s with valid "
"certificate but not from a permitted source "
"address (%.200s).", loc, pw->pw_name, remote_ip);
auth_debug_add("%s: Your address '%.200s' is not "
"permitted to use this certificate for login.",
loc, remote_ip);
return -1;
}
}
/*
*
* XXX this is spammy. We should report remotely only for keys
* that are successful in actual auth attempts, and not PK_OK
* tests.
*/
auth_log_authopts(loc, opts, 1);
return 0;
}
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